Lonnie,
It is likely to be X-10, Insteon, Zwave, or similar devices. They each have their own controller that usually interfaces with the computer. A signal is sent from the computer to the controller, in turn to the module of hardware device that is plugged in or perhaps directly wired into a switch or receptacle to which a lamp or radio or TV or appliance is plugged. Said appliance is then turned on or off.
With some systems one can tell it to dim the lights to a percent of brightness or to have porch lights turn on at 5:30 PM and off at 11:00 PM like a timer.
Just the tip of the home automation / control iceberg.
There are lots of home automation sites on YouTube. Do a search for X-10, Insteon, Hal2000, Homeseer, Vera (home automation) Zwave, and more.
Hope this helps.